This was weird - for some reason, this little brown thing caught my eye because of a tiny movement. I thought maybe it was a fledgling bird, so I got closer for a better look. Turns out, it was a bag of catepillers (or worms?), and one of them was doing some sort of signalling work - its bottom half was hugging the rest of the mass of worms, but its top half was extended at a 90 degree angle from them, and was precicely moving back and forth, like a tiny wave.